Modeling and Analysis of MRR in WEDMed WC-CO Composite by Response Surface Methodology

Wire electro discharge machining (WEDM) was applied to machine tungsten carbide-cobalt (WC-CO) metal matrix composite. It finds increasing application in auto, aeronautical and oil drill application. The material is extremely hard, brittle and tool grade. The present work is undertaken on 10% cobalt, 90% tungsten grade in which keen study is lacking. Amongst many variables, On-time, Off-time and ignition current were shortlisted as critical input parameters. The goal is to identify the input parameter level that maximizes the material removal rate. The input parameters for the experiments were selected after considering previous related work, manufacturer's catalog and industrial expert's opinion. From Taguchi L27 experimental plan, the Box-Behnken trials for 14 experiments were derived in order to model and to predict the output response with good accuracy. The investigation was carried out on the high speed Sodick machine so that it aligns with industry requirement of higher productivity. Response surface modeling and regression analysis was done. Analysis of variance was used to isolate parameters that are critical from pooled data. The experimental results were verified by running at recommended setting of the findings. The outcome was encouraging. Output response improves with on-time at 8 μ- Sec, off -time 15 μ- Sec and ignition current of 16 amperes. It was found that overall metal removal rates increased by 13%, to 17.42 mm3/min from the process average rate of 15.15 mm3/min. A mathematical equation was derived to predict performance. Surface, response contour plots were utilized to analyze performance. The validity of derived model was verified. Since error obtained was 4.5%, higher coefficient of determination is 87% and adequate precision was >4, the model is valid.